Effect of bioplastics on the growth rate and gene transcription levels of marine microalgae.
Supervisor: Eider Bilbao (UPV/EHU)
The continuing nature of plastics and the difficulties or lack for their treatment in wastewater plants lead to the widespread presence of plastics in marine debris, significantly impacting marine organisms, including microalgae, which are vital for aquatic ecosystems. Due to such environmental issues, bioplastics have emerged as an alternative to conventional plastics, although their overall environmental impact is still debated. In this context, this study investigated the toxicity of a range of concentrations of different nanosized bioplastics: partially bio-based pressure-sensitive adhesives (PSA1 and PSA2 and their surfactant DOWFAX) and polylactic acid (PLA nanoparticles and fluorescent PLA) on two marine microalgae species, Tisochrysis lutea and Oltmanssiellopsis sp., by using and comparing the validation criteria of two different toxicity assays commonly used, the OECD Nº201 (OECD, 2011) and the ISO 10253 (ISO,1995). Since the OECD Nº201 (OECD, 2011) protocol demands more restrictive controls than the ISO 10253 (ISO, 1995) which is more accommodating and required fewer assays, results on the average specific growth rate of microalgae were based on the OECD Nº201 (OECD, 2011) procedure. PSA1 and PSA2 did not affect the growth of the naked microalgae Oltmannsiellopsis; on the contrary, T. lutea was sensitive to 1 mg/L and 50 mg/L of PSA2 and to 0.0192 mg/L and 1.92 mg/L of DOWFAX, however, PSA1 did not alter their growth. Exposure to PLAs, did not alter any growing pattern. In conclusion, bioplastics tested did not affect significantly microalgae growth but further species-specific responses and investigating a broader range of bioplastic formulations and environmental conditions as well as potential impacts of long-term usage of bioplastics are needed to contribute more extensive ecological risk assessments.

Keywords: bioplastics, microalgae, PSA, PLA, DOWFAX, toxicity, T.lutea, Oltmannsiellopsis